Whats the cost of realignment with Invisalign?

Invisalign is NOT the only clear aligner system on the market. Invisalign is the Klenex of clear orthodontic aligners. For the problem you are describing (minor recrowding of lower anterior teeth) Invisalign might just be overkill. Get several opinions on your treatment, including from doctors who have more tools in their bag then just Invisalign.

By the way, minor crowding is not only an esthetic issue but very much a health issue as well. The long-term favorable prognosis of straight teeth is far better than for crooked teeth.

Good luck!

I would still recommend doing both upper and lower while achieving your perfect smile. There could be slight problems with your upper teeth that you cant see as a patient...

I sounds like you've had "relaspe" of lower incisor crowding.  This is often a minor problem that can be dealt with in a number of ways, from braces to Invisalign to simple retainers.  You should see an orthodontist who is familiar with a variety of appliances to find out which one will be the best for you.  You might be surprised to discover that correcting your problem may not be as expensive as you thought.